just pretend there is a ruler in our frame of reference. the electron who is moving 0.6c to it, sees the 30cm ruler contract to 24cm. we see the 30cm ruler as 30 cm.
the electron is travelling in its inertial frame. the world around him is moving at 0.6c
if the contracted length of the world around him is 0.24m, that makes his distance 0.3m